Hydraulic brakes



June 12, 1956 J. L. GASSOT 2,750,008

HYDRAULIC BRAKES Filed D80. 11, 1953 2 Sheets-Sheet l I A u/ #5 E 6X. 0 .5 6 $07.

4 TTORNE Y5.

June 12, 1956 R. J. L. GASSOT 2,750,008

HYDRAULIC BRAKES Filed Dec. 11, 1953 2 Sheets$heet 2 A rrys.

United States Patent HYDRAULIC BRAKES Ren Jean Louis Gassot, Paris, France Application December 11, 1953, Serial No. 397,585

Claims priority, application France December 17, 1952 8 Claims. (Cl. 188--90) The present invention constitutes a series of improvements to the hydraulic brakes forming the subject of U. S. Patent No. 2,512,248 in the name of Gassot in which the principle and the general operation have been described.

The object of the present invention is to provide an improved construction wherein provision is made for equalizing forces tending to urge the vanes against the walls of their channels thereby to reduce friction and make the vanes easier to move.

According to the present invention, the hydraulic brake comprises a circular rotor, a circular stator arranged concentrically within' the rotor and defining therewith a circular passage which is filled with hydraulic fluid, said stator having arcuate channels disposed in a radical plane and opening at both their ends into the passage between the stator and rotor, lugs secured internally on the rotor and extending completely across said passage and forming a sliding seal with the stator, arcuate vane members slidably housed within the channels of the stator and movable between an inoperative position wherein they areentirely contained Within the stator and an operative position wherein they extend partially out of the stator across the passage defined between the stator and rotor so as to tend to block flow of the hydraulic fluid, along the passage, caused by movement therein of the lugs as the rotor is rotated, said vane members being provided with cavities in each of their arcuate surfaces forming a sliding bearing against the walls of the respective channel, said vane members also having passage means communicating between surfaces of the vane exposed in the passage to pressure of the driven hydraulic fluid and the cavities to equalize the forces acting in the radial plane of the cavities to press the vane against the walls of its channel in the stator, whereby to facilitate movement of the vanes, and hydraulically operable driver piston means arranged slidably in bores in the stator and coupled tangentially to the vanes for driving the vane into the passage against the pressure of the hydraulic fluid therein acting against the end of the vane moved into the passage.

An example of construction of the fluid-pressure brake is hereinafter particularly described with reference to the accompanying drawings, wherein:

Fig. l is a partial vertical section of the stator with a vane in non-braking position.

Fig. 2 is a partial vertical section showing a vane in braking position.

. Fig. 3 is a transverse section of the rotor and stator to show release means for the vane.

Fig. 4 shows diagrammatically a brake with two lugs and three vanes.

, Figs. 5 and 6 show diagrammatically how a lug causes the return of a vane into its housing.

'Fig. 7 is a transverse section of the rotor and stator toillustrate a cooling system.

Fig. 8 is a partial transverse section to illustrate a mechanical locking means.

Fig. 9 is a partial transverse section to illustrate a safety control.

Fig. 10 is a partial diagrammatic elevation illustrating a foot pedal control.

Fig. 11 is a vertical section showing a driver piston with alarger top.

Fig. 12 is a partial transverse section which shows a movable housing for vanes and joints.

Fig. 13 is a diagrammatic section which shows a modified foot pedal control.

Fig. 14 is a section which shows an automatic valve for feed of a locking system.

Fig. 15 shows schematically a further embodiment of pedal control.

In order to simplify the manufacture and the operation of the vanes (which are designated as vanes 8, 9, 10 and 11 in U. S. Patent No. 2,512,248), and to reduce the dimensions of the brake, whilst modifying in a favourable manner the point of application of the force exerted on the brake hub, these vanes are constituted by a section of a crown 1 (Fig. 1) which moves with slight friction (by the surfaces 48, 49, 50, 51, 52, Fig. 1) in a housing 4 defined by the parts 2 and 3 of the body of the brake drum.

At each side the housing 4 is closed by webs 39 and 40, Figure 3. The vane slides with slight friction against these webs 39 and 40.

In order to explain the operation of this vane system which remains in its housing 4 when no braking occurs, one of the vanes 1 has been shown in operation, i. e. in raised position, in Fig. 2, when it causes the braking action.

In the channel 5, which is defined by the immovable hub of the brake and the movable drum 6, assembled in such a manner as to be as liquid tight as possible, there is placed a liquid which fills all the spaces including cavities A, B, C, D, E, F of the vane 1.

A lug 7 occupies the width of the channel 5. It is integral with the drum 6, and when this drum 6 turns it pushes the liquid forwards in the channel 5 (in the direction of the arrow in Fig. 2).

The vane 1 opposes the passage of the liquid more or less according to whether it is more or less raised by its driver piston 12 controlled by the brake pedal. This causes a pressure in the part of the liquid comprised between this vane 1 and the lug 7. This pressure acting against the surface of the lug 7 produces the braking (because the lug is integral with the drum which itself is secured to the object to be braked).

In order to allow the lug 7 to pass above the vane, the latter has to return into its housing 4. However, the support of the pressure which exists in the channel 5 would make the movements of the vane (which need to be very easy to perform) more diflicult. To obviate this, means have been provided to eliminate all effects of this pressure.

For this purpose the vane 1 (Fig. 2) supporting the pressure on its surfaces 15, 16 and cavities A and B (when the lug 7 moves in the direction of the arrow) is provided with conduits 8 and 9 which permit the liquid of the channel 5 to transmit the pressure into cavity C.

This cavity C is designated to counterbalance entirely I the opposite pressure on 15, 16, A, B.

' channel 5 tending to cause it to retract into its housing.

This force is counteracted by that transmitted by the driver piston 12 which tends to raise the vane 1.

The effect sought is produced in this manner:

The driver piston 12 is coupled to the control channel 30 filled with a liquid on which the brake control pedal exerts a pressure (e. g. by means of a hydraulic brake control of known kind).

The pressure in the control conduit 30 remains constant for any one position of the brake pedal. This is obtained by one or several compensating pistons 69 (Fig. 13) in compensating cylinders opening into control conduit 30, the pistons 66) beingunder the pressure of springs 61 (or any other suitable resilient means). If any variation of pressure occurs in conduit 30, movement of compensation piston 60 will correct it. (Spring 61 can be adjusted in order to modify the pressure admissible in control conduit 30, and this will modify the brake pressure if desired.)

Under the pressure caused in the conduit 30 by the operation of the braking pedal the driver piston 12 coupled to the vane 1 raises this latter and all the other vanes which are not prevented from doing so by the lug or lugs 7.

The vane 1, by progressively obstructing the braking channel 5, creates a pressure in this channel 5.

As the vane 1 is perfectly balanced it could completely close the channel and cause blowing out of the brake but (Figs. 1 and 2) an extra surface 48 has been added to the vane. The pressure which exists in channel 5, when the lug 7 moves in the direction of the arrow) is exerted upon the surface 48 and tends to push the vane 1 into its housing 4.

The vane pushed up by the driver piston 12 will remain at the position wherein pressure on the surface 48 is counterbalanced by the force exerted by the driver piston 12.

As the driver piston 12, governed from the control conduit 30, is pushed up by a constant pressure, for the particular position of the brake pedal, the vane 1 will assume a position which will maintain in the channel 5 a constant pressure whatever the circumstances may be (variation of speed of the liquid in channel 5, small leakages, variation in viscosity of the liquid etc.). This constancy of pressure in channel 5 automatically brings the uniform deceleration essential particularly for motor car brakes, and will prevent any explosion arising from Montgolfiers ram effect.

This constant pressure in channel 5 will permit also the subtraction of a certain amount of the liquid from this channel to cool it, as will be explained more fully hereinafter.

A constant pressure may be obtained also by an automatic valve placed on the lug 7 and which will allow at a certain pressure a part of the liquid of channel 5 to pass by at the rear of said lug. v

In order that no variation of fluid may occur in the control conduit 30, particularly when a driver piston 12 is pushed back as the vane comes back into its housing, a release piston or pistons 17, Fig. 3, is placed in a release cylinder communicating with the control conduit 30. The piston 17 rests, by means of a roller 41, against an axially acting cam 13 which is fixed on the drum 6 and revolves with it. 7

This cam 13 is so shaped that, at the moment when a vane is driven inwardly by a lug 7 moving with the rotor, the vane engages against the driver piston 12 and pushes the latter into its housing, the cam 13 allowing the release piston 17 to move to the right in Fig. 3 to compensate for the decrease of volume caused by movement of piston 12. After the lug 7 has passed over the vane, the release piston 17 is pushed back to the left by cam 13 and this causes the driver piston 12 to rise again. 1

This device permits the reduction of the number of vanes in a brake.

In U. S. Patent No. 2,512,248, four vanes were necessary for each lug. In the present system the number of vanes is only equal to the number of lugs plus one. It means that with the four vanes of the brake of U. S. Patent No. 2,512,248, with the same dimensions, the present brake could at the same pressure, be three times more powerful.

Fig. 4 is a schematic drawing showing a brake with two lugs and only three vanes.

In order to arrive at this result, vanes and lugs are disposed in equidistant manner (for the vanes with respect to the drum 6) and a calculation is made that the total length of a lug shall be comprised, between two successive vanes, as many times as there are lugs plus the space through which the lug moves when the vane withdraws.

Under these conditions therefore an unlimited number of lugs can be used.

In the above-mentioned U. S. patent the return of the vanes into their housing 4 is obtained by a cam. At high speed this may cause shocks, noise, and wear.

In this patent application means are provided to obtain the withdrawal of the vanes without a cam and without shocks.

In Figs. 5 and 6, the lug 7 moving in the direction of the arrow commences by obstructing one of the extremities 14 of the housing 4 of the vane 1.

Continuing its movement, the lug 7 opens the extremity 14 of the housing 4. At this moment the vane 1 supports the pressure of the channel 5 on its surface 15 but the opposite surface 16 is not exposed to the pressure, being behind the lug 7. The vane is then pushed back before any shock may occur with lug 7. In the opposite direction (in a motor car moving in reverse gear for example), the vane returns with the aid of a cam 18 formed on the lug 7 combined with the above described effect of the release piston 17 and the pressure in the top of the driver piston 12.

Means are provided for assuring, for the brake, a mechanical locking in order to permit the immobilisation of the vehicle for long periods, e. g. on hilly roads.

This device can only operate when the brake is only turning at a speed which is substantially zero.

In order to obtain this result, there is used the pressure of the channel 5 which diminished considerably as soon as the vehicle is substantially halted, and which is opposed to the constant pressure created in the control conduit 30 by manipulation of the brake pedal.

For this purpose (Fig. 8), in the lug 7 there is an intake 26 for fluid which carries the pressure of the channel 5 through the conduit 28 to a cylinder where it acts upon a cam pusher piston 27.

Fig. 14 is a central section through a lug 7. In order to provide for both directions of rotation, a passage 26 is provided at one end and a passage 26a at the other end, both these passages communicating with the conduit 28. A ball valve 54 is disposed in the common chamber 54a and, according to the direction of movement of the lug 7, closes off one or other of the passages 26, 26a so that the pressure existing in the channel 5 is transferred to the conduit 28.

The piston (or pistons) 27 is so designed that during the braking it pushes back without effort, by means of the cam 13, the release piston (or pistons) 17.

The cam 13 thus presses against the hub 3 of the brake whilst permitting the release piston 17 to play its part as described above.

The cam 13 is provided in addition with a series of teeth 48.

When the pressure in the Channel 5 becomes small the release piston or pistons 17 are enabled .to push back piston or pistons 27 by means of the cam 13, which in doing so meshes its teeth 48 with other teeth 29 integral with the stator.

The teeth 48 are so shaped that as soon as the pressure on the release piston 17 is relaxed (as the brake is no longer operated) and the drum 6 begins to turn, they free themselves.

The cam 13 is provided additionally with a sealing member 36 which, when the teeth 48 and 29 mesh, presses on another sealing member 36 secured on the stator, reinforcing the fluid-tightness when the brake stops. The cam 13 is rendered fluid-tight with respect to the drum 6 by a flexible packing joint (not shown) which couples it to the drum.

The hydraulic control of the brake has been seen above.

Means are likewise provided for controlling the brake by cable.

This might be combined with a safety device which would operate the brake in case of breakage of the cable control means. A description is given hereinafter of the cable system.

In Fig. 9 there is shown a cable 33. This cable is actuated by the brake pedal 49 of Fig. which maintains it normally under tension with the aid of a spring 56. The cam 50 on which rests a roller 34 on which cable 33 is secured, is designed such that when the pedal 49 is pushed down the cable 33 is progressively released. By means of lever 32, this cable 33 prevents a master piston 43 for each brake, pushed by a spring 34, from closing a maintenance opening 31 and thereafter causes pressure in the control conduit 30 giving braking action. When the cable 33 is released, in the above manner, or when a breakage occurs, the brake is then operated.

As the vanes undergo, according to the amount by which they are raised, a stronger and stronger pressure, the brake control has a variable leverage (either by lever or cam) in such a manner that at the beginning of the action of the pedal the leverage is less than at the end.

Fig. 10 shows a hydraulic control. The pedal 49 pushes the roller 45 fixed to the master piston 35 (corresponding to the piston 43 of Fig. 9) by means of a cam 50 shaped in such a manner as to obtain a greater and greater leverage.

Fig. 12 is a transverse section of the members 2 and 3 which between them define the housing for the vane 1 to move in. The upper member 2 is separate from the lower member 3 and can be slidably moved axially with respect thereto, within limits. This allows the member 2 to follow any slight axial deformations which may exist in the rotor 6. To obtain a seal between the member 2 and the rotor 6 there is provided, at each side of the member 2, a peripheral packing ring 37 and 38.

A part of the liquid contained in the channel 5 is allowed to escape to be cooled during the braking action. To this eifect, Fig. 7, a liquid port 19 which can be disposed in the lug 7 at the position where the braking pressure is produced is normally closed by a ball 24 pushed by a spring 25.

When the drum turns, the centrifugal force permits the ball 24 to uncover the port 19 by compressing the spring 25. When braking occurs the liquid passes through the conduit 19 into one of the sides 20 of the brake. This side of the brake comprises a conduit 21 designed to lead part of the liquid out of the passage to be cooled. This conduit 21 is of such a size as to cause a considerable reduction in the pressure of the liquid, which pressure is only suflicient to assure circulation of liquid. The liquid then passes into a radiator 22 then, cooled, returns through the conduit 21b of the other side of the brake 23 from where it passes, by means of the depression which is produced at the rear of the lug, and by centrifugal force, again into the passage 5 at the opposite side to that at which it passed out.

The return of the liquid taking place under lower pressure, these return conduits are made larger.

Such a system can be provided for cooling the liquid when the brake operates for backwards running. A valve (not shown) placed at the rear of lug 7 then would be arranged to close conduit 21b as soon as the pressure developed there. The radiator 22 may be independent or again may be associated with that of the motor of the vehicle. It is likewise foreseen that the circulation and the ventilation of the radiator may be carried out by an independent motor, even when the vehicle is at rest.

I claim:

1. A hydraulic brake comprising a circular rotor, a circular stator arranged concentrically within the rotor and defining therewith a circular passage which is filled with hydraulic fluid, said stator having arcuate channels disposed in a radial plane and opening at both their ends into the passage between the stator and rotor, lugs secured internally on the rotor and extending completely across said passage and forming a sliding seal with the stator, arcuate vane members slidably housed within the channels of the stator and movable between an inoperative position wherein they are entirely contained within the stator and an operative position wherein they extend partially out of the stator across the passage defined between the stator and rotor so as to tend to block flow of the hydraulic fluid, along the passage, caused by movement therein of the lugs as the rotor is rotated, said vane members being provided with cavities in each of their arcuate surfaces forming a sliding bearing against the walls of the respective channel, said vane members also having passage means communicating between surfaces of the vane exposed in the passage to pressure of the driven hydraulic fluid and the cavities to equalize the forces acting in the radial plane of the cavities to press the vane against the walls of its channel in the stator, whereby to facilitate movement of the vanes, and hydraulically operable driver piston means arranged slidably in bores in the stator and coupled tangentially to the vanes for driving the vane into the passage, against the pressure of the hydraulic fluid therein acting against the end of the vane moved into the passage.

2. A hydraulic brake, as claimed in claim 1, including means for hydraulic operation of the driver piston means comprising a master piston movable in a fluid-filled master cylinder coupled to the driver piston bores, a compensation cylinder communicating with the master cylinder, and a compensating piston in said compensation cylinder having spring-loading arranged to urge it into the compensating cylinder.

3. A hydraulic brake, as claimed in claim 1, wherein the stator has a fluid-filled release cylinder bore communicating with each driver piston bore, a release piston being slidably arranged in each such release cylinder bore, axially acting cam means arranged to bear against each release piston and being provided on the drum at such positions with respect to the lugs as to allow movement of the release pistons to increase the free volume of the release cylinder bore, as each lug comes adjacent to a vane, sufficiently for withdrawal of the driver piston to allow the associated vane to return fully into its channel in the stator.

4. A hydraulic brake, as claimed in claim 3, wherein the cam means are axially movable and are under two opposed axially acting forces constituted respectively by the pressure of hydraulic fluid in the driver piston bore acting on the release piston and the pressure of the hydraulic fluid in the passage and between a vane and a lug, the cam means and the stator being provided with interengageable teeth such that when the rotor is at rest the braking pressure will serve to move the cam to engage the teeth and lock the rotor to the stator.

5. A hydraulic brake, as claimed in claim 1, wherein means for hydraulic operation of the driver piston means comprise a fluid-filled master cylinder in communication with the driver piston means, a master piston in the master cylinder, means resiliently urging the master piston into the master cylinder to increase pressure therein, and control means adjustably restraining the master piston.

6. A hydraulic brake, as claimed in claim 5, wherein the control means comprise a foot pedal for an operator spring'loaded towards oil position, a cam on the pedal, and a cam follower enacting therewith and coupled by cable to the master piston, the cam and cam follower being arranged such that movement of the foot pedal against its spring-loading allows the cable to move in the direction to allow the master piston to move to increase pressure in the master cylinder' 7. A hydraulic brake, as claimed in claim 1, wherein means for hydraulic operation of the driver piston means comprise a fluid-filled master cylinder in communication with the driver pistons, a master piston in the master cylinder, a pivoted foot pedal, a cam on said pedal, and a cam follower for said cam coupled to the master piston, the cam and cam follower being arranged such that on operation of the foot pedal the cam follower drives the 15 2,666,342

References Cited in the file of this patent UNITED STATES PATENTS 1,923,115 Rash et a1 Aug. 22, 1933 2,529,540 Cornwall v Mar. 14, 1950 Bell Jan. 19, 1954 

